1. Field of the Invention
The invention relates to a process for synthesizing high molecular weight hydroxamic acids and other substituted amides on polyacrylic acid latex backbones. The invention further relates to a method of clarifying Bayer process liquors using the substituted amides produced by the process.
2. Description of the Prior Art
The preparation of hydroxamated polymers is well known in the art as disclosed in U.S. Pat. No. 4,902,751, the disclosure of which is incorporated herein by reference. However, when polymers produced by the '751 process have been utilized in Bayer process streams, it has been observed that polymers which contained a higher percentage of residual acrylamide functional groups were not as effective as those polymers in which the acrylamide had more fully hydrolyzed to acrylate.
An alternative method of synthesizing these polymers is disclosed in U.S. Pat. No. 4,868,248. The '248 patent discloses a method of synthesizing high molecular weight hydroxamic acid polymers on a polyacrylic acid backbone, thereby eliminating all acrylamide functional groups from the polymer chain. However, these polymers once again suffered from latex stability problems, especially with respect to the use of polyacrylic acid suspensions or emulsions as an initial building block.
Desirably, a method would exist which would allow the synthesis of stable high molecular weight hydroxamic acid polymers and other substituted amides which could be adopted for use as clarifying aids in Bayer process streams.